Field of the Invention
This invention relates to the field of equipment and accessories of internal combustion engines, more particularly those supplied by high-pressure fuel rails.
More particularly, the invention has as its object a functional air-supply module of such an engine that incorporates a fuel rail.
Description of the Related Art
In internal-combustion-engine vehicles, whose various pistons are supplied by a common fuel rail, the latter is often located close to the intake distributor or a similar supply element (compressor, . . . ) in the immediate vicinity of the engine, these two accessories having further to be rigidly attached to the engine block.
Consequently, it was obvious for a person skilled in the art to try to connect these two components or at least parts of these components to one another so that they form a structural unit having internal cohesion and can be secured together with the engine block. Various solutions in this direction have already been formulated and presented.
Thus, it has been proposed to mount the fuel rail on the distributor, for example by the document FR 2 779 681.
In this document, the two accessories are connected to one another by a quick connection. Nevertheless, an indirect attachment of the fuel rail onto the engine block through the distributor is necessarily less rigid and less strong than a direct attachment and also, in an additional manner, puts stress on at least a part of said distributor, as well as on its attachment points.
By the document WO 2011/036410, in the name of the applicant, an improved attachment mode has been proposed.
This document discloses a functional module incorporating an intake distributor with an integrated attachment and connection plate, a fuel rail, and a retention part for the locking of the rail.
In this design, the distributor participates positively in the holding of the fuel rail by the retention part and therefore has a shape and a structural strength suited to fulfilling this additional function.
It has also been proposed to attach the distributor and the fuel rail in a combined and totally interdependent way at the same attachment points, while ensuring a mechanical connection between the two elements.
Thus, the document EP 1 240 423 discloses a combined distributor-fuel rail unit, in which said rail is provided with annular extensions in the form of holding-down clamps each enclosing a pipe of the distributor. These holding-down clamps formed on the rail are equipped with support feet for the passage of attachment screws, which all line up with openings for attachment of the connection plate of the pipes and which come into contact under pressure on said plate at said openings during mounting on the engine block.
In another form of embodiment disclosed by this document, the holding-down clamps are made in one single independent piece, not having support lugs, covering the connection plate of the pipes, to close at the top the housing for receiving the rail in the plate and to attach the latter to the cylinder head under pressure to achieve airtightness.
In the two embodiments, the set of attachment points of the plate of the pipes and holding-down clamps are combined, and the latter are not in direct support on the engine block, but rest on the plate that they secure and hold flat by clamping, also using the rail, against said engine block.
For this reason, the attachment of the holding-down clamps and the attachment of the pipes are totally interdependent, and the fuel rail itself contributes to the mounting with locking of said pipes on the engine block.
Such a construction nevertheless involves a complex structure for the fuel rail when it is formed in one piece with the holding-down clamps, since the latter must engage the various portions of the pipe.
In addition, these known embodiments call for a forced configuration for the connection plate of the pipes for the purpose of achieving a total lining-up between support feet of the holding-down clamps and fastening openings of the plate of the pipes. The result can be an establishment of the attachment sites at the connection plate that is not optimized in terms of strains and stresses, especially since this plate is assembled with the intake manifold, whose positioning in the space of the main body can be offset or out-of-line relative to that of the plate.
Furthermore, stressing the fuel rail to participate positively in the securing of the plate of the pipes on the engine block generates mechanical stresses at this rail, which can be detrimental over time to its structural integrity, taking into account in particular the vibratory environment.
Finally, a necessary separation of the plate of the pipes during a separation or disassembly of the holding part may not be desirable in certain constructive configurations and may even be detrimental, for example in terms of time loss, difficulties during reassembly, and/or of airtightness.
In line with the document EP 1 240 423, the document EP 1 270 917 also presents a combined attachment solution of a plate of an intake distributor and a fuel rail, in which the rail ensures the retention and attachment of the plate.
For this reason, the fuel rail exhibits a complex structure and must be adapted to bear the resulting stresses of these additional functions of retention and attachment.
Finally, in the design proposed by the document US 2005/045155, the distributor consists of two parts, namely a lower part forming the attachment and connection plate, and an upper part forming the body of the distributor as such.
In this design, the retention of the fuel rail is performed directly and solely by the body of the distributor, the plate providing bracket supports for said rail (not direct attachment of the latter on the cylinder head). The distributor must therefore have a shape and structural strength suited to this additional function.